Differences in heart rate variability associated with long-term exposure to NO2.
BACKGROUND
Heart rate variability (HRV), a measure of cardiac autonomic tone, has been associated with cardiovascular morbidity and mortality. Short-term studies have shown that subjects exposed to higher traffic-associated air pollutant levels have lower HRV.


OBJECTIVE
Our objective was to investigate the effect of long-term exposure to nitrogen dioxide on HRV in the Swiss cohort Study on Air Pollution and Lung Diseases in Adults (SAPALDIA).


METHODS
We recorded 24-hr electrocardiograms in randomly selected SAPALDIA participants >or= 50 years of age. Other examinations included an interview investigating health status and measurements of blood pressure, body height, and weight. Annual exposure to NO2 at the address of residence was predicted by hybrid models (i.e., a combination of dispersion predictions, land-use, and meteorologic parameters). We estimated the association between NO2 and HRV in multivariable linear regression models. Complete data for analyses were available for 1,408 subjects.


RESULTS
For women, but not for men, each 10-microg/m3 increment in 1-year averaged NO2 level was associated with a decrement of 3% (95% CI, -4 to -1) for the standard deviation of all normal-to-normal RR intervals (SDNN), -6% (95% CI, -11 to -1) for nighttime low frequency (LF), and -5% (95% CI, -9 to 0) for nighttime LF/high-frequency (HF) ratio. We saw no significant effect for 24-hr total power (TP), HF, LF, or LF/HF or for nighttime SDNN, TP, or HF. In subjects with self-reported cardiovascular problems, SDNN decreased by 4% (95% CI, -8 to -1) per 10-microg/m3 increase in NO2.


CONCLUSIONS
There is some evidence that long-term exposure to NO2 is associated with cardiac autonomic dysfunction in elderly women and in subjects with cardiovascular disease.
Felber Dietrich
Denise
D
Institute of Social and Preventive Medicine, University of Basel, Basel, Switzerland. denise.felber@unibas.ch
Gemperli
Armin
A
Gaspoz
Jean-Michel
JM
Schindler
Christian
C
Liu
L-J Sally
LJ
Gold
Diane R
DR
Schwartz
Joel
J
Rochat
Thierry
T
Barthélémy
Jean-Claude
JC
Pons
Marco
M
Roche
Frédéric
F
Probst Hensch
Nicole M
NM
Bridevaux
Pierre-Olivier
PO
Gerbase
Margaret W
MW
Neu
Urs
U
Ackermann-Liebrich
Ursula
U
D000328:Adult; D000393:Air Pollutants / Q000633:toxicity*; D015331:Cohort Studies; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D009585:Nitrogen Dioxide / Q000633:toxicity*
D000393:Air Pollutants; D009585:Nitrogen Dioxide